A rare drought in 2005 - billed as a once-in-a-hundred-years event - was then followed by another drought in 2010 that may have been even worse, according to a study by a team of British and Brazilians scientists in the journal Science. With a huge number of trees dying as a result of the droughts, the scientists predict that the Amazon will not be able to absorb as much carbon dioxide from the atmosphere as usual in future.

This would remove an important global buffer against pollution. Even worse, rotting trees may release into the atmosphere as much as five billion tons of C02 in the coming years. That would be almost as much as the 5.4 billion tons emitted from fossil fuel use by the US in 2009.

Based on the impact of the dry spell on tree deaths in 2005, the team projected that "Amazon forests will not absorb their usual 1.5 billion tons of CO2 from the atmosphere in both 2010 and 2011", the study said.

A new study, funded by Nasa, has found that the most serious drought in the Amazon for more than a century had little impact on the rainforest's vegetation Photo: REX

The United Nations' climate change panel is facing fresh criticism after new research contradicted the organisation's claims about the devastating effect climate change could have on the Amazon rainforest.

A new study, funded by Nasa, has found that the most serious drought in the Amazon for more than a century had little impact on the rainforest's vegetation.

The findings appear to disprove claims by the Intergovernmental Panel on Climate Change (IPCC) that up to 40% of the Amazon rainforest could react drastically to even a small reduction in rainfall and could see the trees replaced by tropical grassland.

The IPCC has already faced intense criticism for using a report by environmental lobby group WWF as the basis for its claim, which in turn had failed to cite the original source of the research.

Boston) -- A new NASA-funded study has concluded that Amazon rain forests were remarkably unaffected in the face of once-in-a-century drought in 2005, neither dying nor thriving, contrary to a previously published report and claims by the Intergovernmental Panel on Climate Change.

"We found no big differences in the greenness level of these forests between drought and non-drought years, which suggests that these forests may be more tolerant of droughts than we previously thought," said Arindam Samanta, the study's lead author from Boston University.

The comprehensive study published in the current issue of the scientific journal Geophysical Research Letters used the latest version of the NASA MODIS satellite data to measure the greenness of these vast pristine forests over the past decade.

A study published in the journal Science in 2007 claimed that these forests actually thrive from drought because of more sunshine under cloud-less skies typical of drought conditions. The new study found that those results were flawed and not reproducible.